Referring to FIG. 1, a conventional four-way radio frequency (RF) power amplifier device includes three identical Wilkinson power dividers 10, 11, 12, four identical power amplification circuits 13, 14, 15, 16, and three identical Wilkinson power combiners 17, 18, 19.
Further referring to FIG. 2, the Wilkinson power divider 10 includes an input line 1010 receiving an RF input signal (Pi) that has a wavelength of λ, two quarter wave lines 1020, 1030, a resistor 1060, and two output lines 1040, 1050. The quarter wave lines 1020, 1030 each have a length of λ/4, and divide the RF input signal (Pi) into two first RF division signals (Pio). The output lines 1040, 1050 are respectively coupled to the quarter wave lines 1020, 1030 to output the first RF division signals (Pio). The resistor 1060 is coupled between the quarter wave lines 1020, 1030 to enhance isolation and prevent the first RF division signals (Pio) from interfering with each other. Having identical structure as the Wilkinson power divider 10, the input lines of the Wilkinson power dividers 11, 12 are respectively coupled to the output lines 1040, 1050 of the Wilkinson power divider 10 for receiving the first RF division signals (Pio), thereby dividing the first RF division signals (Pio) into four second RF division signals (P) that have the same voltage amplitude and the same phase. Since the input line and the output lines of each of the Wilkinson power dividers 10-12 are only used as connection terminals, their lengths would be minimized in design, so the lengths of the input line and the output lines can be ignored in comparison to the quarter wave lines.
The power amplification circuits 13-16 respectively receive the second RF division signals (P), perform power amplification on the second RF division signals (P), and output RF amplification signals (As). Each of the Wilkinson power combiners 17-19 is configured to be the same as the Wilkinson power divider 10, but is used in a reverse way for power combination. The Wilkinson power combiners 17-19 cooperatively combine the RF amplification signals (As) into an RF output signal (Po).
Such a conventional RF power amplifier device uses three Wilkinson power dividers and three Wilkinson power combiners, leading to a large chip area and a longer signal transmission path. The quarter wave lines 1020, 1030 are configured jointly as a rectangle-like shape that has several right angles, which may result in unsmooth signal transmission and greater power loss during generation of the RF output signal (Po). Greater power loss may cause lower power gain between the RF output signal (Po) and the RF input signal (Pi), thereby reducing power-added efficiency (PAE) of the RF power amplifier device.